Identification of sources and groundwater recharge zones from hydrochemistry and stable isotopes of an agriculture-based paleo-lacustrine basin of drought-prone northeast Mexico

Abstract

Over exploitation for agricultural activities and consumption has depleted the groundwater resources of drought-prone northeast Mexico. Major ion concentrations along with δ18OH2O, δ2HH2O and d-excess values of shallow groundwater from the Cieneguilla Basin (near Tula) located at a distance of ∼200 km from coast of the Gulf of Mexico helped to contribute new data about drought vulnerability in this region through identification of the moisture source and groundwater recharge zone. Different degrees of rock-water interaction through gypsum, anhydrite and halite dissolutions and minor silicate weathering controlled the hydrochemistry. Stable isotopes yielded a least square regression and slope similar to the local as well as global meteoric water lines, indicating minimal effect of evaporation during the recharge as well as in the subsoil. Isotopic fractionations along with a digital elevation model demarcated the recharge zones at north and east of the basin, with altitudinal difference of ≥1000 m, and indicated that the recharge occurred through warm season moisture sourced from the Gulf of Mexico. Less frequent landfalling of tropical storms caused by warmer sea surface temperature, however, has reduced this rainfall over the last few decades. If the trend of global warming continues unabated, the depleted groundwater resources would trigger reduction in agricultural activities in this drought-prone region and lead to enhanced socio-economic challenges.